Short Answer
Overview
The major third is an interval that separates two notes by four semitones, or two whole steps. In the system of twelve-tone equal temperament that dominates modern Western music, the interval measures exactly 400 cents. In just intonation, the most consonant tuning of a major third has a frequency ratio of 5:4, giving it a slightly brighter quality than the equal‑tempered version.
Because a major third sits at the heart of the major triad (root‑third‑fifth), it is a primary building block of major chords, scales, and tonal progressions. The interval can be heard in countless melodies and harmonies, from classical sonatas to contemporary pop songs, and it contributes to the perception of brightness and stability in music.
History / Origin
The term “third” dates back to medieval modal theory, where intervals were counted by the number of letter names they spanned. The qualifier “major” emerged in the Renaissance as theorists such as Gioseffo Zarlino distinguished between the larger, more consonant version of the third (now called major) and the smaller, minor third. The modern definition solidified during the common‑practice period (c. 1650–1900) as tonal harmony standardized the major triad.
How It’s Used
Major thirds appear in a variety of contexts. In harmony, they form the upper structure of major chords (e.g., C‑E‑G) and are stacked to create extended chords such as major sevenths (C‑E‑G‑B). In melodic writing, a leap of a major third often conveys a sense of uplift or optimism. The interval is notated on staff by placing the two notes a third apart, and in chord symbols it is indicated by the “maj” or by the absence of a “–” sign (e.g., Cmaj, C). Instruments ranging from piano and guitar to brass and voice employ the major third both as a harmonic device and as a melodic interval.
Why It Matters
Understanding the major third is essential for performers, composers, and listeners because it defines the tonal character of major chords and scales. The interval’s clear, consonant sound helps establish the key center and influences emotional perception; a major third often feels bright, whereas its minor counterpart feels darker. Iconic examples include the opening of Beethoven’s “Symphony No. 5” (the famous “short‑short‑short‑long” motif begins with a major third), the chord progression in The Beatles’ “Let It Be,” and the melodic leap in the jazz standard “Autumn Leaves.”
Common Misconceptions
A major third is the same as a perfect fourth.
A major third spans four semitones (400 cents), while a perfect fourth spans five semitones (500 cents); they are distinct intervals with different harmonic functions.
All thirds sound the same in any tuning system.
In just intonation a major third has a 5:4 ratio, which is slightly narrower and more consonant than the equal‑tempered 400‑cent version used in most modern instruments.
The term “major third” refers to a specific chord shape on the guitar.
“Major third” describes an interval between two pitches; while guitarists may use particular fingerings, the concept applies to any instrument.
FAQ
How many cents is a major third in equal temperament?
In twelve‑tone equal temperament a major third measures exactly 400 cents, which is four semitones.
What is the just‑intonation ratio for a major third?
The most consonant just‑intonation major third has a frequency ratio of 5:4, meaning the higher pitch vibrates at five times the frequency of the lower pitch divided by four.
Can a major third be inverted?
Yes. Inverting a major third (raising the lower note by an octave) yields a minor sixth, an interval of nine semitones.
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